Abstract
Coastal megaclast deposits are dominated by detrital particles larger than 1 m in size. These attract significant attention of modern researchers because of the needs of sedimentary rock nomenclature development and interpretation of storm and tsunami signatures on seashores. If so, finding localities that exhibit coastal megaclast deposits is an important task. Field studies do not offer a quick solution, and, thus, remote sensing tools have to be addressed. The application of the Google Earth Engine has permitted to find four new localities, namely Hondarribia in northern Spain (Biscay Bay), the Ponza Island in Italy (Tyrrhenian Sea), the Wetar Island in eastern Indonesia (Banda Sea), and the Humboldt o Coredo Bay at the Colombia/Panama border (eastern Pacific). In these localities, coastal megaclast deposits consisting of blocks (1–10 m in size) and some megablocks (>10 m in size) are delineated and preliminary described in regard to the dominant size of particles, package density, mode of occurrence, etc. The limitations of such virtual surveys of coastal megaclast deposits are linked to an insufficiently high resolution of satellite images, as well as ‘masking’ effects of vegetation cover and cliff shadows. However, these limitations do not diminish the importance of the Google Earth Engine for finding these deposits. Consideration of some tourism-related information, including photos captured by tourists and bouldering catalogues, facilitates search for promising areas for subsequent virtual surveying of megaclast distribution. It is also established that the Google Earth Engine permits quantitative analysis of composition of coastal megaclast deposits in some areas, as well as to register decade-long dynamics or stability of these deposits, which is important to interpret their origin. The current opportunities for automatic detection of coastal megaclast deposits seem to be restricted.
Highlights
Coastal sediment dynamics is always highly complex, and, it provides a lot of issues for geoscience investigations
An interest in nomenclature development for large clasts that started near the end of the 20th century [1] and attention to coastal hazards facilitated by the Indian Ocean Tsunami of 2004 [2] have shaped a new international research direction, namely megaclast studies [3]
The objective of the present paper is to demonstrate the application of the Google Earth Engine for finding coastal megaclast deposits on the basis of several representative examples
Summary
Coastal sediment dynamics is always highly complex, and, it provides a lot of issues for geoscience investigations. Megaclasts of ocean and sea coasts have been investigated most intensively These studies have been conducted in so different places of the world as Baja California in Mexico [4,5], North Eleuthera of the Bahamas [6,7], and Rabat in Morocco [8]. The works have tended to focus on only some regions like the Mediterranean (e.g., [9,10,11,12,13]), the global evidence of large clast accumulations has become huge already, and it continues growing. This evidence requires extension and generalization for further conceptual treatment. Coastal megaclast deposits of Quaternary age are of special importance because the evidence of such deposits from the earlier geological periods remains scarce [3,15]
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